Clinical and biological aspects of Philadelphia-negative/BCR-negative chronic myeloid leukemia

Molecular subtypes predict therapeutic responses and identifying and validating diagnostic signatures based on machine learning in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a hematological tumor derived from hematopoietic stem cells. The aim of this study is to analyze the biological characteristics and identify the diagnostic markers of CML. We obtained the expression profiles from the Gene Expression Omnibus (GEO) database and identified 210 differentially expressed genes (DEGs) between CML and normal samples. These DEGs are mainly enriched in immune-related pathways such as Th1 and Th2 cell differentiation, primary immunodeficiency, T cell receptor signaling pathway, antigen processing and presentation pathways. Based on these DEGs, we identified two molecular subtypes using a consensus clustering algorithm. Cluster A was an immunosuppressive phenotype with reduced immune cell infiltration and significant activation of metabolism-related pathways such as reactive oxygen species, glycolysis and mTORC1; Cluster B was an immune activating phenotype with increased infiltration of CD4 + and CD8 + T cells and NK cells, and increased activation of signaling pathways such as interferon gamma (IFN-γ) response, IL6-JAK-STAT3 and inflammatory response. Drug prediction results showed that patients in Cluster B had a higher therapeutic response to anti-PD-1 and anti-CTLA4 and were more sensitive to imatinib, nilotinib and dasatinib. Support Vector Machine Recursive Feature Elimination (SVM-RFE), Least Absolute Shrinkage Selection Operator (LASSO) and Random Forest (RF) algorithms identified 4 CML diagnostic genes (HDC, SMPDL3A, IRF4 and AQP3), and the risk score model constructed by these genes improved the diagnostic accuracy. We further validated the diagnostic value of the 4 genes and the risk score model in a clinical cohort, and the risk score can be used in the differential diagnosis of CML and other hematological malignancies. The risk score can also be used to identify molecular subtypes and predict response to imatinib treatment. These results reveal the characteristics of immunosuppression and metabolic reprogramming in CML patients, and the identification of molecular subtypes and biomarkers provides new ideas and insights for the clinical diagnosis and treatment.

Molecular Pathogenesis of BCR-ABL-Negative Atypical Chronic Myeloid Leukemia

Atypical chronic myeloid leukemia is a rare disease whose pathogenesis has long been debated. It currently belongs to the group of myelodysplastic/myeloproliferative disorders. In this review, an overview on the current knowledge about diagnosis, prognosis, and genetics is presented, with a major focus on the recent molecular findings. We describe here the molecular pathogenesis of the disease, focusing on the mechanisms of action of the main mutations as well as on gene expression profiling. We also present the treatment options focusing on emerging targeted therapies.

Atypical chronic myeloid leukemia: a rare entity with management challenges

The aim of our study was to review the clinicopathologic features and management of atypical chronic myeloid leukemia (aCML). Relevant manuscripts published in English were searched using PubMed. aCML is diagnosed as per WHO 2016 classification in the presence of leukocytosis ≥13 × 109/l with circulating neutrophil precursors ≥10%, monocytes less than 10%, minimal basophils, hypercellular bone marrow with granulocytic proliferation and dysplasia, bone marrow blast less than 20% and absence of BCR/ABL fusion gene. Common cytogenetic features and mutations include trisomy 8, and mutations in SETBP1 and ETNK1. Median survival is 1-2 years. Hematopoietic stem cell transplant may be the only curative option. Ruxolitinib and dasatinib are emerging therapeutic options. Thus, aCML is a rare entity with poor survival. Novel therapies are needed.

Chronic myelomonocytic leukemia and atypical chronic myeloid leukemia: novel pathogenetic lesions

Chronic myelomonocytic leukemia (CMML) and atypical chronic myeloid leukemia (aCML) are distinct, yet related, entities of myelodysplastic/myeloproliferative neoplasms (MDS/MPN) characterized by morphologic dysplasia with accumulation of monocytes or neutrophils, respectively. Our understanding of the molecular pathogenesis of CMML and aCML has advanced, mainly due to the application of novel technologies such as array-based karyotyping and next-generation sequencing. In addition to previously known recurrent aberrations, somatic uniparental disomy affecting chromosomes 3, 4, 7, and 11 frequently occurs in CMML. Novel somatic mutations of genes, including those associated with proliferation signaling (CBL, RAS, RUNX1, JAK2 (V617F)) and with modification of epigenetic status (TET2, ASXL1, UTX, EZH2) have been found. Various combinations of mutations suggest a multistep pathogenesis and may account for clinical heterogeneity. Most recently, several spliceosome-associated-gene mutations were reported and SRSF2 mutations are frequently detected in CMML. The prognostic and diagnostic significance of these molecular lesions, in particular their value as biomarkers of response or resistance to specific therapies, while uncertain now is likely to be clarified as large systematic studies come to completion.

Chronic neutrophilic leukaemia: an Egyptian case

Chronic neutrophilic leukaemia (CNL) is a rare myeloproliferative disorder of elderly patients characterised by sustained neutrophilia. The diagnosis of CNL requires the exclusion of BCR/ABL positive chronic myelogenous leukaemia and leukemoid reaction. We present here a case of a 61-year-old Egyptian man with CNL and 21 months of follow-up. The main symptom of our patient was purpura. Splenomegaly, hepatomegaly and lymph node enlargement were not detected at presentation or throughout the patient's course. Thrombocytopenia was a considerable problem in our patient, causing recurrent bleeding and affecting the hydroxyurea dose adjustment. While hydroxyurea decreased the total leucocytic count, it could not affect the fatal course of the disease. The survival course of our patient extended to 21 months after presentation. The cause of death was attributed to disease progression.

Differential diagnostic challenge of chronic neutrophilic leukemia in a patient with prolonged leukocytosis

Our interesting case deals with the clinical and morphological aspects of a chronic neutrophilic leukemia and the critical evaluation of differential diagnosis of leukemoid reaction in bone marrow biopsies.

Outcome of hematopoietic stem cell transplantation in patients with atypical chronic myeloid leukemia

Atypical chronic myeloid leukemia (aCML) occurs rarely and is associated with a poor prognosis when treated with conventional chemotherapy. We evaluated the outcome of aCML after allogeneic hematopoietic stem cell transplantation (HSCT). Nine patients were transplanted from HLA-identical siblings (n = 4), HLA-compatible unrelated donors (n = 4) or twin brother (n = 1). Median follow-up was 55 months after transplant (range, 9.1-118.1 months). One patient who was transplanted in advanced disease with bone marrow from his twin brother relapsed 19 months post transplant. This patient was successfully retransplanted from the original donor. All patients remained in complete remission. Analysis of the leukocyte chimerism of peripheral white blood cells and bone marrow buffy coat cells by VNTR-polymerase chain reaction (PCR) and single-nucleotide polymorphism real-time PCR revealed complete chimerism in all patients who had received an allogeneic transplant. One patient suffering from cerebral toxoplasmosis died 9 months post transplant. All other patients were alive at the time of analysis. Our findings suggest that the outcome of allogeneic or syngeneic transplantation in patients with aCML may not be worse than the outcome of transplantation for BCR-ABL-positive CML.

A 2-year-old with atypical CML with a t(5;12)(q33;p13) treated successfully with imatinib mesylate

Atypical chronic myelogenous leukemia (aCML) is a myelodysplastic/myeloproliferative disorder that usually occurs in older adults. Here we report a pediatric patient with aCML and a t(5;12)(q33;p13) with a corresponding fusion gene ETV6-PDGFRB. Because the PDGFRB tyrosine kinase is one of the known targets of tyrosine kinase inhibitors, this patient achieved cytogenetic and molecular remission with treatment with imatinib mesylate (formerly STI571; now Gleevec in the United States and Glivec in Europe). This case illustrates one of many myelodysplastic/myeloproliferative disorders that can be treated with this particular tyrosine kinase inhibitor.

Cytogenetics of chronic myeloproliferative disorders and related myelodysplastic syndromes

The only MPD associated with any specific chromosome anomaly is CML, which is linked with t(9;22)(q34;q11.2) or a variant of this anomaly. An association exists for del(13)(q12q14) and CIMF; t(5;12)(q33;p13) and CEL; and del(20q11), +8, and +9 and PV, but these anomalies can be seen in various hematologic malignancies. The most common chromosomal anomalies among MPD in order of frequency are t(9;22)(q34;q11.2), -Y, +8, +9, -7, del(20) (q11q13), del(13)(q12q14), del(5)(q13q33), and del(12)(p12). FISH techniques are useful for MPD to study inadequate bone marrow or blood specimens and to monitor disease status among patients with known chromosome anomalies, but they are not more sensitive than conventional chromosome studies.

Pathology of the myeloproliferative diseases

The classification of myeloid neoplasms now includes CMPD, mixed CMPD/ MDS, MDS, and acute myeloid leukemias. CMPD and CMPD/MDS, both clonal stem cell diseases, share myeloproliferative features, including typical hypercellular marrows, organomegaly, and cell lineage maturation. The CMPD generally differ by which myeloid cell lineage dominates hematopoiesis, and the main diseases include CML, PV, ET, and CIM. The mixed CMPD/MDS disorders also show dysplastic features and variable amounts of effective hematopoiesis; these disorders include CMML, JMML, and atypical CML. Given the overlap in morphology among these diseases, correlation with clinical, hematologic, and cytogenetic/molecular genetic findings is imperative for precise classification.

The occurrence of Philadelphia chromosome (Ph) negative leukemia after hematopoietic stem cell transplantation for Ph positive chronic myeloid leukemia: implications for disease monitoring and treatment

Chronic myeloid leukemia (CML) is a clonal neoplastic disorder, characterized by t(9;22)(q34;q11) that results in the formation of the Philadelphia chromosome (Ph) and the BCR/ABL fusion gene. Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for CML. Much of its therapeutic efficacy is attributed to a graft-versus-leukemia (GVL) effect exerted by donor-derived lymphoid cells against the Ph positive (Ph+) clone. Post-HSCT monitoring by cytogenetic and molecular detection of the Ph+ clone is necessary, so that pre-emptive immunologic or pharmacologic treatment may be administered at an early stage of relapse. However, under rare circumstances a second Ph negative (Ph-) leukemia may evolve post-HSCT. The pathogenetic possibilities included leukemia arising from donor-derived hematopoietic stem cells (HSCs), or transformation of residual recipient-derived Ph- HSCs that have survived the conditioning chemotherapy and radiotherapy. Recipient-derived Ph- leukemia may be related to genetic alterations that precede the onset of CML, or myelotoxic effects of the HSCT conditioning regimen. The diagnosis of Ph- relapses requires detailed investigations by conventional karyotyping, fluorescence in-situ hybridization (FISH), and molecular analysis; as well as chimerism studies that help to document the donor or recipient origin of the leukemia. Although uncommonly reported in the past, Ph- relapses may in fact be more frequent if leukemic relapses post-HSCT are more thoroughly evaluated with these investigations. The recognition of Ph- relapses are important in several ways. Ph- relapses cannot be identified by monitoring investigations targeting the Ph+ clone, so that the early detection of Ph- leukemia is usually not possible. Furthermore, Ph- relapses will not respond to therapeutic strategies effective against the Ph+ CML clone.

Characteristics and outcome of patients with Philadelphia chromosome negative, bcr/abl negative chronic myelogenous leukemia

BACKGROUND

Up to 5% of patients with chronic myelogenous leukemia (CML) do not have the Philadelphia (Ph) translocation t(9;22)(q34;q11) or a bcr/abl molecular rearrangement. Although the diagnostic criteria of this entity are still under debate, there is general agreement that patients with Ph negative, bcr/abl negative CML have a severe clinical course that is not affected significantly by current treatment options.

METHODS

A population of 76 patients with bcr/abl negative CML who had received minimal or no previous therapy was characterized carefully with the intent of investigating clinical and hematologic variables and their association with survival by univariate, correlation, and multivariate analyses. A group of 73 patients with Ph negative CML who were not tested for the bcr/abl rearrangement (bcr/abl unknown) was analyzed separately and used for extension of the analysis.

RESULTS

In the bcr/abl negative patient population, the median overall survival was 24 months. At the time of the analysis, 38 patients (50%) had died, and blastic transformation preceded death in 31%. Chromosomal abnormalities were found in 30% of the 76 patients, with trisomy 8 the most common abnormality. Complex chromosomal abnormalities were rare, and monosomy 7 was not observed. Survival was not affected significantly by treatment. Multivariate analysis identified older age (> 65 years), anemia (hemoglobin < 10 g/dL), and severe leukocytosis (white blood cells > 50 x 10(9)/L) as variables with independent prognostic significance for poor survival. A prognostic scoring system stratified patients into a low-risk group (53%) and a high-risk group (47%), with median survivals of 38 months and 9 months, respectively.

CONCLUSIONS

Bcr/abl negative CML is a distinct clinical entity associated with very poor prognosis. Two risk categories are identifiable using a simple scoring system based on age, hemoglobin level, and leukocyte number.

Philadelphia (Ph) chromosome-positive chronic myeloid leukaemia relapsing as Ph-negative leukaemia after allogeneic bone marrow transplantation

Two patients with Philadelphia chromosome-positive (Ph(+)) chronic myeloid leukaemia (CML) relapsed 1.5 and 5 years after allogeneic bone marrow transplantation (BMT). Although the leukaemias were of recipient origin, t(9;22) could no longer be detected using conventional cytogenetics/fluorescence in situ hybridization or molecularly. Both patients responded to immunotherapy with donor lymphocytes/peripheral blood stem cells, although one patient ultimately relapsed again. These patients were similar to the occurrence of Ph(-) leukaemias previously described in Ph(+) CML after treatment with interferon or autologous BMT, and might be relevant in the pathogenesis and monitoring of treatment after BMT in CML.

BCR rearrangement-negative chronic myelogenous leukemia revisited

PURPOSE

To document the characteristics of patients with major breakpoint cluster region (M-bcr) rearrangement-negative chronic myelogenous leukemia (CML).

PATIENTS AND METHODS

The hematopathologist, who was blinded to patients' molecular status, reviewed the referral bone marrows and peripheral-blood smears from 26 patients with Philadelphia (Ph) translocation-negative CML who lacked Bcr rearrangement (and other evidence of a Bcr-Abl anomaly) and 14 patients (controls) with chronic-phase Ph-positive CML. Clinical data was ascertained by chart review.

RESULTS

Among the 26 M-bcr rearrangement-negative CML patients, three pathologic subtypes emerged: (1) patients indistinguishable from classic CML (n = 9), (2) patients with atypical CML (n = 8), and (3) patients with chronic neutrophilic leukemia (n = 9). Among the 14 patients with Ph-positive CML who were included in the blinded review, 13 were classified as classic CML, and one was classified as atypical CML. The only statistically significant difference between M-bcr rearrangement-negative subgroups was in the proportion of patients having karyotypic abnormalities, an observation common only in patients with atypical CML (P = 0.008). However, the small number of patients in each subgroup limited our ability to differentiate between them. Interferon alfa induced complete hematologic remission in five of 14 patients; four of these remissions lasted more than 5 years. Only one of 26 patients developed blast crisis. The median survival of the 26 patients was 37 months.

CONCLUSION

Patients with M-bcr rearrangement-negative CML fall into three morphologic subgroups. Disease evolution does not generally involve blastic transformation. Instead, patients show progressive organomegaly, leukocytosis, anemia, and thrombocytosis. Some patients in each subgroup can respond to interferon alfa.

Atypical chronic myeloid leukaemia with trisomy 21 mosaicism as a sole chromosomal abnormality

We present a 46-year-old patient with Ph-chromosome negative, bcr-negative chronic myeloid leukaemia (CML) in accelerated phase with a clonal trisomy 21 in the leukaemic blast cells. A rapid progress of disease with appearance of monocytosis is described, showing similar features to chronic myelomonocytic leukaemia (CMML). Heterogeneous characteristics and possible distinction of these two entities are discussed.

Atypical chronic myelogenous leukemia following immunosuppressive therapy for severe aplastic anemia

Late clonal complications of aplastic anemia (AA) such as acute leukemia, myelodysplastic syndromes or paroxysmal nocturnal hemoglobinuria have been recognized for a long time. To our knowledge, chronic myelogenous leukemia (CML) as a late complication of severe aplastic anemia has as yet not been reported. We report here a case of AA treated successfully with antilymphocytic globulin and cyclosporin in whom Ph1 negative, BCR/ABL negative CML developed 8 years after diagnosis of AA. This case of atypical, secondary CML was refractory to treatment with interferon alpha and hydroxyurea.

Atypical chronic myeloid leukemia with der(20)t(17;20)(q21;q13)

We present a case of atypical chronic myeloid leukemia that developed blastic transformation four months after initial presentation, with the blast cells showing multilineage antigen expression. A novel karyotypic abnormality, der(20)t(17;20)(q21;q13), was found in bone marrow cells at diagnosis. The potential role of such an aberration in leukemogenesis is discussed.

Translocation (4;15)(p16;q24): a novel reciprocal translocation in a patient with BCR/ABL negative myeloproliferative syndrome progressing to blastic phase

A patient with BCR/ABL negative myeloproliferative syndrome with a 46,XY,del(3)(q21), t(4;15)(p16;q24) karyotype is described. Fluorescence in situ hybridization performed with chromosomes 4 and 15 painting probes confirmed a novel reciprocal (4;15) translocation. The absence of crkl tyrosine phosphorylation, no activation of the abl kinase as measured by autophosphorylation, and a normal-size abl transcript suggest an alternative mechanism for leukemogenesis to that operative in Ph positive BCR/ABL positive chronic myeloid leukemia. A number of genes potentially relevant to tumorigenesis, some involving the ras signaling pathway, map to the 4p16 and 15q24 chromosome regions.